A mechanism of the described type is known from U.S. Pat. No. 4 663 917. Furthermore, DE-OS 37 32 033 shows a similar sealing mechanism.
The stripper rods are, in the known mechanisms, connected to a drive mechanism which at the same time is used to move the cross-sealing jaws. Thus, it is practically not possible to move the stripper rods independently of the cross-sealing jaws. From this results the disadvantage that the cross-welding system having the cross-sealing jaws must also have the stripper rods. It is not possible with this drive-like coupling to provide any type of sequential movement for the stripper rods and the cross-sealing jaws. This is particularly annoying with respect to the movement of the cross-sealing jaws and the stripper rods in longitudinal direction of the foil tube. The crosssealing jaws must be moved together with the foil tube during the duration of the sealing without a relative movement occurring between the sealing jaws and the tube. Compared to this, it is unavoidable in the case of the stripper rods to provide a relative movement between the foil tube and the rods in order to compress the material in the tube which is to be packaged downwardly into the bag, and to free the welding area of the foil tube from the material to be packaged.
A further disadvantage of the so far known constructions is that, in particular, the design of the drive of the cross-sealing jaws cannot be changed independently from the stripper mechanism so that, as this is shown in U.S. Pat. No. 4 663 917, the cross-sealing jaws must be pivoted together with the stripper mechanism. A rotating design of the cross-sealing jaws is thereby not possible. Here problems arise regarding the masses to be moved and the occurring vibrations. A similar situation is true for the mechanism known from DE-OS 37 32 033, in which both the cross-welding jaws and also the stripper mechanism must be moved in the circular curved track. Problems result during rotation of these mechanisms with respect to acceleration and deceleration, which problems are also enhanced by the relatively large rotating masses.
The invention relates furthermore to a stripper mechanism for a tubular bag packaging machine comprising two stripper tools arranged on both sides of the path of movement of the tubular bag, which stripper tools can be moved by means of a drive mechanism.
In a tubular bag packaging machine, a foil strip is guided over a forming shoulder and is formed into a tube by means of a longitudinal seam sealing mechanism, which tube encloses a fill pipe or a format pipe through which the product to be packaged can be guided into the interior of the foil tube. The individual bags containing the product are each closed off by means of a bottom and a top seam, creating thereby in each case simultaneously the top seam of the preceding bag and the bottom seal of the next following bag. A mechanism of this type is known for example from U.S. Pat. No. 4 663 917.
U.S. Pat. No. 4 391 081 shows a stripper mechanism for a tubular bag packaging machine in which the movement of the stripper tools and of the cross-welding jaws is coupled with one another. The cross-welding jaws are movable through a four-bar mechanism or scissors mechanism, with the up and down movement of the stripper tools being caused by the opening and closing movement of the cross-welding jaws. This development of the invention does not make it possible to adjust and optimize the stripping operation with respect to the sealing operation because of the rigid coupling of the up and down movement of the stripper tools.
It is necessary during the construction of the top seam and of the bottom seam by means of a pair of cross-sealing jaws to keep the sealing area of the foil tube free of residues of the material to be packaged. In particular in the case of bulky material, as for example potato chips, there exists the risk that after the bag is closed off by the bottom seam and filled, the bag still being open at the top, the product does not evenly fall into the bag. Stripper tools are used for this reason, which, usually in the form of a pair of beams, are moved downwardly along the bag in order to transport the product completely into the bag and out of the area of the bottom and top seam.
Caused by the technical sequence of such a tubular bag packaging machine, in which the foil tube moves essentially continuously through the machine, it is necessary that the stripper mechanism be designed so that in its sequence of movement the stripper tools, in addition to the speed of movement of the foil tube, can carry out a stripping movement. Furthermore, it is necessary because of this type of a system to carry out the stripping operation in the closing area of the cross-sealing jaws. The stripper mechanism must thus be moved into the open space formed between the crosssealing jaws and the foil tube with the cross-sealing jaws being open. The stripper tools are thereafter closed and are thus placed against the foil tube and are thereafter moved downwardly. This assures that during the use of the stripper mechanism the cross-sealing jaws must remain open. The available station time thus limits the cross-sealing time and the time during which the stripper mechanism is in operation.
The basic purpose of the invention is to provide a stripper mechanism of the described type, which has a drive which is independent of the cross-sealing jaws, and which with a simple design and reliable applicability can be utilized in any desired types of tubular bag packaging machines.
The invention has the further purpose of providing a stripper mechanism of the mentioned type which, with a simple design and reliable applicability, enables an adjustment of the speed of movement of the stripper mechanism so that the time for the stripping operation and the sealing operation can be maximized.